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Formation of an Intramolecular Periplasmic Disulfide Bond in TcpP Protects TcpP and TcpH from Degradation in Vibrio cholerae.
Morgan, Sarah J; French, Emily L; Thomson, Joshua J; Seaborn, Craig P; Shively, Christian A; Krukonis, Eric S.
Affiliation
  • Morgan SJ; Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
  • French EL; Department of Biomedical and Diagnostic Sciences, University of Detroit Mercy School of Dentistry, Detroit, Michigan, USA.
  • Thomson JJ; Department of Biomedical and Diagnostic Sciences, University of Detroit Mercy School of Dentistry, Detroit, Michigan, USA.
  • Seaborn CP; Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
  • Shively CA; Program in Cell and Molecular Biology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
  • Krukonis ES; Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA Department of Biomedical and Diagnostic Sciences, University of Detroit Mercy School of Dentistry, Detroit, Michigan, USA krukones@udmercy.edu.
J Bacteriol ; 198(3): 498-509, 2016 02 01.
Article in En | MEDLINE | ID: mdl-26574510
ABSTRACT
UNLABELLED TcpP and ToxR coordinately regulate transcription of toxT, the master regulator of numerous virulence factors in Vibrio cholerae. TcpP and ToxR are membrane-localized transcription factors, each with a periplasmic domain containing two cysteines. In ToxR, these cysteines form an intramolecular disulfide bond and a cysteine-to-serine substitution affects activity. We determined that the two periplasmic cysteines of TcpP also form an intramolecular disulfide bond. Disruption of this intramolecular disulfide bond by mutation of either cysteine resulted in formation of intermolecular disulfide bonds. Furthermore, disruption of the intramolecular disulfide bond in TcpP decreased the stability of TcpP. While the decreased stability of TcpP-C207S resulted in a nearly complete loss of toxT activation and cholera toxin (CT) production, the second cysteine mutant, TcpP-C218S, was partially resistant to proteolytic degradation and maintained ∼50% toxT activation capacity. TcpP-C218S was also TcpH independent, since deletion of tcpH did not affect the stability of TcpP-C218S, whereas wild-type TcpP was degraded in the absence of TcpH. Finally, TcpH was also unstable when intramolecular disulfides could not be formed in TcpP, suggesting that the single periplasmic cysteine in TcpH may assist with disulfide bond formation in TcpP by interacting with the periplasmic cysteines of TcpP. Consistent with this finding, a TcpH-C114S mutant was unable to stabilize TcpP and was itself unstable. Our findings demonstrate a periplasmic disulfide bond in TcpP is critical for TcpP stability and virulence gene expression. IMPORTANCE The Vibrio cholerae transcription factor TcpP, in conjunction with ToxR, regulates transcription of toxT, the master regulator of numerous virulence factors in Vibrio cholerae. TcpP is a membrane-localized transcription factor with a periplasmic domain containing two cysteines. We determined that the two periplasmic cysteines of TcpP form an intramolecular disulfide bond and disruption of the intramolecular disulfide bond in TcpP decreased the stability of TcpP and reduced virulence gene expression. Normally TcpH, another membrane-localized periplasmic protein, protects TcpP from degradation. However, we found that TcpH was also unstable when intramolecular disulfides could not be formed in TcpP, indicating that the periplasmic cysteines of TcpP are required for functional interaction with TcpH and that this interaction is required for both TcpP and TcpH stability.
Subject(s)

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Bacterial Proteins / Transcription Factors / Vibrio cholerae / Gene Expression Regulation, Bacterial / Fimbriae Proteins Language: En Journal: J Bacteriol Year: 2016 Document type: Article Affiliation country: United States

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Bacterial Proteins / Transcription Factors / Vibrio cholerae / Gene Expression Regulation, Bacterial / Fimbriae Proteins Language: En Journal: J Bacteriol Year: 2016 Document type: Article Affiliation country: United States
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